Finite Element Analysis of Posterior Atlantoaxial Fixationfor Type II Odontoid Process Fracture with High-Riding Vertebral Artery
Dong Ziqiang1, Zhao Gaiping1*, Bi Houhai1, Zhao Qinghua2, Wang Hongjie2
1(School of Medical Instrument and Food Engineering University of Shanghai for Science and Technology,Shanghai 200093,China) 2(Department of Orthopaedics,Shanghai First People′s Hospital,Shanghai 200080,China)
Abstract To investigate the biomechanical characteristics on the treatment of type II odontoid process fracture with axial unilateral high-riding vertebral artery by two kinds of the combined posterior atlantoaxial fixation,the stability of the upper cervical vertebra and the stress distribution of the internal fixation implants translaminar screw,pedicle screws and C2 pars screw were analyzed. Based on the CT image data of type II odontoid process fracture of human cervical spine,combined with the finite element pre-processing software,according to the clinical operation plan,the posterior atlantoaxial fixation models of two combinations of upper cervical vertebra were established:1) unilateral axial translaminar screw + atlantoaxial pedicle screws fixation (C1PS-C2TL+PS);2) unilateral C2 pars screw + atlantoaxial pedicle screws fixation (C1PS-C2pars+PS). The range of motion and the stress distribution of internal fixation implants of two fixed models were analyzed under flexion and extension,lateral bending and rotation. In the two kinds of posterior atlantoaxial fixation on the treatment of type II odontoid process fracture with unilateral high-riding vertebral artery,the range of motion of the atlantoaxial joint of C1PS-C2TL+PS model decreased by 92.71%,91.28%,95.89% respectively under flexion and extension,lateral bending and rotation,and C1PS-C2pars+PS model decreased by 89.50%,94.77% and 92.72% respectively,all of which indicated that the stiffness of the fixed segments of vertebral body was significantly improved. In addition,the stress of C1PS-C2pars+PS model at the root of the axial screw and the lower part of the connecting rod was significantly concentrated under the flexion and extension conditions,with the maximum stress values of 179.9 and 167.6 MPa respectively,which was 55.1 and 52.2 MPa higher than those of C1PS- C2TL+PS model. The maximum stress values of C2pars screw under different conditions changed greatly,the maximum value was 123.7 MPa under flexion condition,which was 21.4 MPa higher than the maximum stress value of C2TL. In conclusion,the two fixed operations of C1PS-C2TL+PS and C1PS-C2pars+PS could effectively improve the stiffness of atlantoaxial for type II odontoid process fracture with high-riding vertebral artery,the former has better stability in flexion and extension and rotation,and the C1PS-C1TL+PS internal fixation is more reasonable in structure and stress distribution. These results provided theoretical basis for the study of internal fixation for type II odontoid process fracture with high-riding vertebral artery.
Dong Ziqiang,Zhao Gaiping,Bi Houhai, et al. Finite Element Analysis of Posterior Atlantoaxial Fixationfor Type II Odontoid Process Fracture with High-Riding Vertebral Artery[J]. Chinese Journal of Biomedical Engineering, 2020, 39(4): 459-465.
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